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13 results on '"Pulkkinen TI"'

1. A Back-tracing Code to Study the Magnetosphere Transmission Function for Primary Cosmic Rays

Author

Pulkkinen, TI, Tsyganenko, NA, Friedel RHW, Bobik, P, Boschini, M, Gervasi, M, Grandi, D, Micelotta, E, Rancoita, P, Boschini, MJ, GERVASI, MASSIMO, Rancoita, PG, Pulkkinen, TI, Tsyganenko, NA, Friedel RHW, Bobik, P, Boschini, M, Gervasi, M, Grandi, D, Micelotta, E, Rancoita, P, Boschini, MJ, GERVASI, MASSIMO, and Rancoita, PG more...

Abstract

We have developed a code to reconstruct the Cosmic Rays trajectory in the Earth magnetosphere. This code solves the Lorentz equation and propagates a particle backward in time. The total magnetic field is evaluated by using the International Geomagnetic Reference Field (IGRF) 2000-2005 and the external magnetic field Tsyganenko-96. This code has been used both for a simulation of randomly generated inputs and for the analysis of the AMS-01 experiment data taken during the STS-91 Space Shuttle mission in June 1998. By a full spectrum simulation we have separated the primary Cosmic Ray component from the secondary one present at the altitude of AMS orbit (400 km). We have built the transmission function in the magnetosphere for 1998 for several regions with different geomagnetic latitude. The same simulation has also been performed for the magnetic conditions of the year 2005, the expected starting time of the long-duration AMS-02 data taking. Then we have estimated the variation of the transmission function with time and obtained the primary Cosmic Ray flux at the altitude of 400 km starting from the flux at 1 AU as predicted by the CREME96 model more...

Published
2005

2. A study of inverted-V auroral acceleration mechanisms using Polar/Fast Auroral Snapshot conjunctions

Author

Janhunen, P, Olsson, A, Peterson, WK, Laakso, H, Pickett, JS, Pulkkinen, TI, Russell, CT, Janhunen, P, Olsson, A, Peterson, WK, Laakso, H, Pickett, JS, Pulkkinen, TI, and Russell, CT

Abstract

We present observations of electrons and ions that have been affected by an auroral plasma acceleration mechanism. In the nine events studied, nearly simultaneous and magnetically conjugate measurements were made by instruments on the Fast Auroral Snapsho, Addresses: Janhunen P, Finnish Meteorol Inst, POB 503, FIN-00101 Helsinki, Finland. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. Swedish Inst Space Phys, S-75591 Uppsala, Sweden. Lockheed Martin Space Phys Lab, Palo Alto, CA USA. Univ Iowa, Dept Ph more...

Published
2001

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3. Two substorm intensifications compared: Onset, expansion, and global consequences

Author

Pulkkinen, TI, Baker, DN, Frank, LA, Sigwarth, JB, Opgenoorth, HJ, Greenwald, R, Friis-Christensen, E, Mukai, T, Nakamura, R, Singer, H, Reeves, GD, Lester, M, Pulkkinen, TI, Baker, DN, Frank, LA, Sigwarth, JB, Opgenoorth, HJ, Greenwald, R, Friis-Christensen, E, Mukai, T, Nakamura, R, Singer, H, Reeves, GD, and Lester, M more...

Abstract

We present observations of two sequential substorm onsets on May 15, 1996. The first event occurred during persistently negative IMF B-Z, whereas the second expansion followed a northward turning of the interplanetary magnetic field (IMF). While the first, Addresses: Pulkkinen TI, Finnish Meteorol Inst, POB 503, FIN-00101 Helsinki, Finland. Finnish Meteorol Inst, FIN-00101 Helsinki, Finland. Univ Colorado, Atmospher & Space Phys Lab, Boulder, CO 80303 USA. Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 more...

Published
1998

4. Auroral precipitation fading before and at substorm onset: ionospheric and geostationary signatures

Author

Kauristie, K, Pulkkinen, TI, Huuskonen, A, Pellinen, RJ, Opgenoorth, HJ, Baker, DN, Korth, A, Syrjasuo, M, Kauristie, K, Pulkkinen, TI, Huuskonen, A, Pellinen, RJ, Opgenoorth, HJ, Baker, DN, Korth, A, and Syrjasuo, M more...

Abstract

Rapid fading of auroral activity a few minutes before substorm breakup has earlier been analyzed in case-studies. Here we report on a study in which all-sky camera (ASC) and magnetic data over 3 years were examined to find breakups that were accompanied b, Addresses: Kauristie K, FINNISH METEOROL INST, DEPT GEOPHYS, FIN-00101 HELSINKI, FINLAND. SWEDISH INST SPACE PHYS, UPPSALA, SWEDEN. UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, BOULDER, CO 80309. MAX PLANCK INST AERON, KATLENBURG DUHM, GERMANY. more...

Published
1997

5. What can we tell about global auroral electrojet activity from a single meridional magnetometer chain?

Author

Kauristie, K, Pulkkinen, TI, Pellinen, RJ, Opgenoorth, HJ, Kauristie, K, Pulkkinen, TI, Pellinen, RJ, and Opgenoorth, HJ

Abstract

The AE indices are generally used for monitoring the level of magnetic activity in the auroral oval region. In some cases, however, the oval is either so expanded or contracted that the latitudinal coverage of the AE magnetometer chain is not adequate. Th, Addresses: Kauristie K, FINNISH METEOROL INST, DEPT GEOPHYS, FIN-00101 HELSINKI, FINLAND. SWEDISH INST SPACE PHYS, UPPSALA, SWEDEN. more...

Published
1996

6. ANALYSIS OF THE SUBSTORM TRIGGER PHASE USING MULTIPLE GROUND-BASED INSTRUMENTATION

Author

KAURISTIE, K, PULKKINEN, TI, PELLINEN, RJ, JANHUNEN, P, HUUSKONEN, A, VILJANEN, A, OPGENOORTH, HJ, HEIKKILA, WJ, BAKER, DN, KAURISTIE, K, PULKKINEN, TI, PELLINEN, RJ, JANHUNEN, P, HUUSKONEN, A, VILJANEN, A, OPGENOORTH, HJ, HEIKKILA, WJ, and BAKER, DN more...

Abstract

During the substorm trigger phase, i.e. during the last few minutes before the onset, the slowly and linearly developing growth phase features strengthen exponentially. Often the enhanced auroral activity fades abruptly during a couple of minutes just pri, Addresses: KAURISTIE K, FINNISH METEOROL INST, DEPT GEOPHYS, POB 503, SF-00101 HELSINKI, FINLAND. SWEDISH INST SPACE PHYS, S-75591 UPPSALA, SWEDEN. UNIV TEXAS, CTR SPACE SCI F022, RICHARDSON, TX 75083. UNIV COLORADO, ATMOSPHER & SPACE PHYS LAB, BOULDER, C more...

Published
1995

7. Near-Earth substorm onset - a coordinated study

Author

Persson, M. A. L., OPGENOORTH, HJ, PULKKINEN, TI, ERIKSSON, AI, DOVNER, PO, REEVES, GD, BELIAN, RD, ANDRE, M, Blomberg, Lars, ERLANDSON, RE, BOEHM, MH, AIKIO, AT, HAGGSTROM, I, Persson, M. A. L., OPGENOORTH, HJ, PULKKINEN, TI, ERIKSSON, AI, DOVNER, PO, REEVES, GD, BELIAN, RD, ANDRE, M, Blomberg, Lars, ERLANDSON, RE, BOEHM, MH, AIKIO, AT, and HAGGSTROM, I more...

Abstract

We present simultaneous satellite and ground-based measurements of a substorm. Throughout the initial substorm expansion, southward drifting arcs are observed poleward of the expanding substorm aurora, indicating two independent systems of particle precipitation. Freja passes the brightening onset arc in the topside ionosphere near the moment of the substorm onset, observing an Alfven wave, field aligned current and oxygen ion outflow. The substorm onset occurs at low magnetospheric L-shells, near the poleward edge of the region of trapped particles. The location and time for the substorm injection are confirmed by geostationary spacecraft together with magnetometers, all-sky cameras and radar on the ground. We believe that the substorm onset may be triggered by modification of the oxygen content of the inner magnetosphere during the growth-phase caused by ionospheric ion outflow., NR 20140805 more...

Published
1994
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8. THE TRIGGER PHASE OF MAGNETOSPHERIC SUBSTORMS

Author

PELLINEN, RJ, PULKKINEN, TI, HUUSKONEN, A, KAURISTIE, K, HEIKKILA, WJ, OPGENOORTH, HJ, PUDOVKIN, M, PELLINEN, RJ, PULKKINEN, TI, HUUSKONEN, A, KAURISTIE, K, HEIKKILA, WJ, OPGENOORTH, HJ, and PUDOVKIN, M more...

Abstract

The last few minutes of the substorm growth phase before the auroral breakup show features distinct both from the gradual growth phase development and from the rapidly evolving expansion phase. During this time the optical auroras fade, energetic particle, Addresses: PELLINEN RJ, FINNISH METEOROL INST, HELSINKI, FINLAND. SWEDISH INST SPACE PHYS, UPPSALA, SWEDEN. UNIV ST PETERSBURG, ST PETERSBURG, RUSSIA. UNIV TEXAS, RICHARDSON, TX 75080. more...

Published
1994

9. A Back-tracing Code to Study the Magnetosphere Transmission Function for Primary Cosmic Rays

Author

Massimo Gervasi, Elisabetta R. Micelotta, D. Grandi, Pier-Giorgio Rancoita, Matteo Boschini, Pavol Bobik, Pulkkinen, TI, Tsyganenko, NA, Friedel RHW, Bobik, P, Boschini, M, Gervasi, M, Grandi, D, Micelotta, E, and Rancoita, P more...

Subjects
Physics, PAMELA detector, FIS/06 - FISICA PER IL SISTEMA TERRA E PER IL MEZZO CIRCUMTERRESTRE, Astrophysics::High Energy Astrophysical Phenomena, Flux, Magnetosphere, Cosmic ray, Astrophysics, Cosmic Ray, Computational physics, law.invention, symbols.namesake, FIS/05 - ASTRONOMIA E ASTROFISICA, Transmission Function, law, Physics::Space Physics, symbols, Geomagnetic latitude, International Geomagnetic Reference Field, Ultra-high-energy cosmic ray, Lorentz force, FIS/04 - FISICA NUCLEARE E SUBNUCLEARE
Abstract

We have developed a code to reconstruct the Cosmic Rays trajectory in the Earth magnetosphere. This code solves the Lorentz equation and propagates a particle backward in time. The total magnetic field is evaluated by using the International Geomagnetic Reference Field (IGRF) 2000-2005 and the external magnetic field Tsyganenko-96. This code has been used both for a simulation of randomly generated inputs and for the analysis of the AMS-01 experiment data taken during the STS-91 Space Shuttle mission in June 1998. By a full spectrum simulation we have separated the primary Cosmic Ray component from the secondary one present at the altitude of AMS orbit (400 km). We have built the transmission function in the magnetosphere for 1998 for several regions with different geomagnetic latitude. The same simulation has also been performed for the magnetic conditions of the year 2005, the expected starting time of the long-duration AMS-02 data taking. Then we have estimated the variation of the transmission function with time and obtained the primary Cosmic Ray flux at the altitude of 400 km starting from the flux at 1 AU as predicted by the CREME96 model. more...

Published
2005

10. Energy Flux Through the Magnetopause During Flux Transfer Events in Hybrid-Vlasov 2D Simulations.

Author

Ala-Lahti M, Pulkkinen TI, Pfau-Kempf Y, Grandin M, and Palmroth M

Abstract

Solar wind-magnetosphere coupling drives magnetospheric dynamic phenomena by enabling energy exchange between magnetospheric and solar wind plasmas. In this study, we examine two-dimensional noon-midnight meridional plane simulation runs of the global hybrid-Vlasov code Vlasiator with southward interplanetary magnetic field driving. We compute the energy flux, which consists of the Poynting flux and hydrodynamic energy flux components, through the Earth's magnetopause during flux transfer events (FTEs). The results demonstrate the spatiotemporal variations of the energy flux along the magnetopause during an FTE, associating the FTE leading (trailing) edge with an energy injection into (escape from) the magnetosphere on the dayside. Furthermore, FTEs traveling along the magnetopause transport energy to the nightside magnetosphere. We identify the tail lobes as a primary entry region for solar wind energy into the magnetosphere, consistent with results from global magnetohydrodynamic simulations and observations., (© 2022. The Authors.) more...

Published
2022
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11. Direct evidence of nonstationary collisionless shocks in space plasmas.

Author

Dimmock AP, Russell CT, Sagdeev RZ, Krasnoselskikh V, Walker SN, Carr C, Dandouras I, Escoubet CP, Ganushkina N, Gedalin M, Khotyaintsev YV, Aryan H, Pulkkinen TI, and Balikhin MA

Abstract

Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom-particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp. more...

Published
2019
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12. Coronal mass ejections and their sheath regions in interplanetary space.

Author

Kilpua E, Koskinen HEJ, and Pulkkinen TI

Abstract

Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs., (© The Author(s) 2017.) more...

Published
2017
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13. Supermagnetosonic jets behind a collisionless quasiparallel shock.

Author

Hietala H, Laitinen TV, Andréeová K, Vainio R, Vaivads A, Palmroth M, Pulkkinen TI, Koskinen HE, Lucek EA, and Rème H

Abstract

The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the following generation mechanism for the jets: The local curvature variations inherent to quasiparallel shocks can create fast, deflected jets accompanied by density variations in the downstream region. If the speed of the jet is super(magneto)sonic in the reference frame of the obstacle, a second shock front forms in the sheath closer to the obstacle. Our results can be applied to collisionless quasiparallel shocks in many plasma environments. more...

Published
2009
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